This invention relates to preparations for smoothing textile fibers, to a process for smoothing textile fibers and to the use of aliphatic polyethers as smoothing agents. This application is related to commonly assigned copending application Ser. No. 159,628, filed on even date herewith.
The combined effect of higher offwinding speeds for yarns and filaments and distinctive and refined techniques for the manufacture of sheet-form textiles has been that the travel characteristics of yarns used in the modern textile industry must meet increasingly stringent requirements. To satisfy these requirements, smoothing and flexibilizing substances have to be applied to the yarns and to the sheet-form materials produced from them to improve their further processing properties. The terms "smoothing agent", "smoothing substance", and "smoothing composition" as used herein mean materials which impart the property of slipperiness to fibers to which they are applied.
The smoothing agents used are required on the one hand to reduce friction both between the individual fibers and between fibers or yarns and metal and, on the other hand, to guarantee satisfactory stitchability of sheet-form textiles. If excessive friction is generated during stitching, stitching damage occurs through filaments being damaged, broken or overheated. The consequences of stitching damage are particularly serious in the case of knitted fabrics because laddering can later occur upon mechanical stressing of the fabric. For this reason, the mobility of the filaments in the stitch network is also of great importance. Reducing the needle penetration forces during sewing on modern high-speed sewing machines has acquired particular significance because high-speed sewing machines operating purely mechanically can make up to 7,000 stitches per minute. However, this requires more vibration-resistant and hence thicker needles which again can easily cause stitch damage.
Paraffins, esters, polyethylenes, silicones and polyalkylene glycols are known smoothing agents as for example disclosed in the publication "Melliand Textilberichte", Vol. 3, pp. 203 to 207 (1977). The effectiveness of these smoothing agents in many cases depends on the nature of the fiber substrate. U.S. Pat. No. 4,474,668 describes polyethylenes as smoothing agents for textile fibers having an average molecular weight of from 3,000 to 8,000, a density of from 0.94 to 1.01, an acid value of from 25 to 60 and a saponification value of from 40 to 80.